Hussey J D, Bishop M J
Division of Respiratory Therapy, Seattle VAMC, USA.
Chest. 1996 Aug;110(2):494-7. doi: 10.1378/chest.110.2.494.
It is occasionally desirable for patients with a tracheostomy tube to breathe through their native airway. We hypothesized that capped tracheostomy tubes with cuffs deflated would create substantial additional resistance to airflow without fenestration but would provide minimal resistance to airflow when the tube had a fenestration.
Two tracheal models were tested simulating a large (26 mm) and an average (18 mm) trachea. Tests were carried out with fenestrated and nonfenestrated tracheostomy tubes of sizes ranging from No. 4 to No. 10. Negative pressure inspiration was simulated using suction.
With a large trachea or small tubes, the suction required to generate flows of 40 L/min or greater remained less than 5 cm H2O with or without a fenestration. However, with an average-sized trachea and no fenestration, the pressure required to generate flows of 40 L/min or greater exceeded 5 cm H2O and with No. 8 or No. 10 tubes exceeded 20 cm H2O. A fenestration routinely reduced the required pressure to less than 5 cm H2O.
The effort required to move gas across the native airway in the absence of a fenestration may be substantial. If a patient is to breathe through a native airway, a fenestrated tube should be used unless the tracheostomy tube is a No. 4.
